Observations

Description

Valves lanceolate-clavate, with headpole rounded and slightly protracted. Footpole rounded. Valve tapers gently towards the headpole, more strongly towards the footpole, especially in shorter specimens. The raphe is undulate and lateral. The axial area is narrow at the poles, straight, widens at the center to form a small, somewhat rounded central area. A single round stigma is found in the central area. Striae are radiate throughout the length of the valve. Longitudinal lines are positioned on either side of the axial area; they are indistinct in some specimens. The apical pore field is small. This species is known only from Montana.

Comments: These metrics for length and breadth indicates valves can be slightly smaller (down to 34 µm in length, and 11 µm in breadth) than indicated in Kociolek et al. (1986)

Valves lanceolate-clavate. Valve tapers gently towards the headpole, more strongly towards the footpole especially in shorter specimens. Longitudinal lines are positioned on either side of the axial area; they are indistinct in some specimens.

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This species has been confused with Gomphoneis eriense var. variabilis, due to the presence of the longitudinal lines close to the axial area. This species differs from the G. eriense var. variabilis by the shape of the valve, and the slightly larger valves (up to 90 µm in length).